AnsweredAssumed Answered

Single motor protection with VFD per Article 430.130

Question asked by tom.brenner on Oct 18, 2019
Latest reply on Oct 22, 2019 by tom.brenner@lenze.com

Looking for interpretation of Article 430.130(A)(1) and (2) with respect to Branch-Circuit Short-Circuit and Ground Fault Protective device rating for single motor applications when a VFD is installed. The article refers back to 430.52 which really addresses manual motor controller and overload relay configurations, limiting the maximum value to 400% of motor full load current (when protected by a non-time delay fuse or circuit breaker). However the VFD in this case provides overload, ground fault and short circuit protection for the motor; the branch circuit protective device protects the VFD.  In some cases, a larger protective device is required for the VFD.  If a higher BCP value has been UL Listed for use with the VFD per UL 61800-5-1 or UL 508C and is specified in the VFD manufacturer's instructions, can this override Article 430.52 and Table 430-52 since overload and short circuit protection is provided by the VFD?

#tomb

Outcomes